The present invention relates to a point-to-multiple points signal transmission system of the type having a central station and several participant stations and by which the transmission channels between the central station and the participants can be apportioned as required.
Point-to-multiple point wireless transmission systems, whether earth-bound or satellite transmission systems, permit new signal connections to be relatively quickly installed or existing connections to be improved. In today's communication systems, one distinguishes between activated traffic connections with fixed or dynamic self changing data rates and packet-oriented traffic connections. The activated traffic connections include, for example, the telephone (analog or digital, POTS or ISDN), facsimile transmissions, data transmissions with a constant data rate over dedicated conduits or the like. Examples of packet-oriented traffic connections data traffic include the LAN-connections, the frame relay service, and, recently, the ATM transmissions; a characteristic of such examples is the burst-type transmission of data packets.
Wireless transmission systems in participant access domains for both types of communication systems should optimally exploit the available frequency spectrum. Ancillary requirements for the transmission are the capability to be as resistant as possible to interferences such as, for example, weather related fading, frequency selective fading, interferences from reflection, interferences from neighboring signal cells, interferences from other signal services, and amplitude-and phase shifting.
The demand for optimization of the available frequency spectrum can be satisfied by the use of a point-to-multiple points signal transmission system. A point-to-multiple points signal transmission system is exemplarily illustrated in Microwave magazine Vol. 10, No. 6, 1984, pages 629-630. Such an arrangement permits the exploitation of the frequency band of the available signal channels through a demand on the required frequency band which occurs only as needed. The {commq} between the central station and the individual participants proceeds through multiple processing in a frequency multiplex (FDMA), in time multiplexing (TMDA), in code multiplexing (CDMA), in space multiplexing (SDMA), or in a mixed form of these processing formats, whereby the frequency channels, the time slots, the {spread codes and the spaced antenna {clubs} can be allocated as desired in accordance with the requirements of the participant.
In German patent document DE 44 26 183 A1, a point-to-multiple points signal transmission system is disclosed in which the transmission capability is flexibly tailored or customized to the requirement of the participant so that the {bandwidth of the individual transmission channel to the individual participants can be arranged relative to the respective data transmission rate. Also, this point-to-multiple points signal transmission system permits an adjustment of the modulation type and the modulation grade (for example, N-PSK, with N=2 . . . 16 or M-QAM with M=4 . . . 256) for the individual transmission channels.